PSI - Issue 80

Seiji Mitsubayashi et al. / Procedia Structural Integrity 80 (2026) 423–430 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 7. SEM images of fracture surfaces for specimens with (A) 1.0 wt% and (B) 1.25 wt% CNF added to PP .

3.3. Interlaminar shear strength of CFRTP Based on the results presented in Sections 3.1 and 3.2, the interfacial shear strength was evaluated for the conditions that exhibited the highest fracture toughness for each additive location. Specifically, measurements were conducted for the condition without CNF addition, for the case in which 0.025 wt% CNF was added to CF, and for the case in which 1.0 wt% CNF was added to PP. The results are shown in Figure 8. In both CNF-added cases, the interfacial shear strength increased compared to the the specimen without CNF. Notably, the specimen with CNF added to PP exhibited a value approximately 18% higher than that with CNF added to CF. These findings suggest that adding CNF to PP more effectively enhances fiber/resin interfacial adhesion, which contributes to improved interlaminar fracture toughness.

Fig. 8. Interfacial shear strength for the condition without CNF addition, with 0.025 wt% CNF added to CF, and with 1.0 wt% CNF added to PP.

4. Conclusion In this study, the effect of the location of CNF addition in CFRTP on fracture toughness was investigated by conducting ENF, ECT, and fragmentation tests using CFRTP with CNF added to PP or CF. As a result, the following findings were obtained. (1) Compared to the specimens without CNF addition, the addition of CNF to either the carbon fiber or the resin led to an improvement in Mode II and Mode III interlaminar fracture toughness.